This invention is directed to a metal diaphragm valve and related structure including a novel multiple ply diaphragm structure and diaphragm plunger means arranged to deflect the diaphragm when it is desired to operate the valve. The invention also includes a novel method of making a composite multiple ply diaphragm structure and, in one embodiment, provides a hermetically sealed valve.
Metal diaphragm valves have found considerable utility as isolating or shut-off valves for toxic or other dangerous fluids and for borated water safety systems in nuclear fueled power generating plants. These valves employ a metal diaphragm member disposed transversely across a cavity in the valve body to provide a metal barrier and thereby seal the fluid present in the body cavity and flow passages on one side of the diaphragm from leakage through or around a valve operating mechanism provided on the other side of the diaphragm. These valves usually include a closure member mounted for axial movement to engage a valve seat on the fluid side of the diaphragm and a diaphragm plunger mounted for movement to contact and deflect the diaphragm and move the closure member to engage the valve seat and close the valve. Certain valves embodying a metal diaphragm member and this general principle of operation are shown in U.S. Pat. No. 2,144,754, issued Jan. 24, 1939; No. 2,277,395, issued Mar. 24, 1942; No. 2,986,372, issued May 30, 1961 and No. 3,126,194, issued Mar. 24, 1964.
Such prior art valves have usually employed a convexly curved or dome-shaped diaphragm with a circumferential edge portion of the diaphragm seated between a shoulder provided to the valve body and an opposing surface of a valve bonnet or cover secured to the body to close the cavity provided therein. The circumferential edge portion of the diaphragm seated between the opposing surfaces presents a potential leakage path across the interface between the fluid side surface of the diaphragm and the oppositely disposed seating surface. Also, if the diaphragm is of diametrically continuous curvature, the oppositely disposed seating surfaces will provide a annular stress region bounding the internal flexing portion of the diaphragm which region is susceptible to cracking after repeated flexure of the diaphragm. The prior art valves have also employed a diaphragm contacting surface of spherical curvature on the plunger which provides a circular diaphragm deflecting pattern. Although a circular deflecting pattern is satisfactory for many types of service, the spherical plunger surface uniformly distorts the entire central area of the diaphragm and provides radially progressive, concentric annular stress areas where stress induced cracking of the diaphragm surfaces may propagate in a circular path around the diaphragm.
With the foregoing considerations in mind, it is a principle purpose and object of this invention to provide a metal diaphragm valve having an improved multiple ply diaphragm structure.
Another object is to provide a method of making an improved dome-shaped multiple ply diaphragm structure.
A further object of this invention is to provide a diaphragm plunger having an improved diaphragm contacting and deflecting surface.
A still further object is to provide a hermetically sealed metal diaphragm valve in which all potential fluid leakage paths are sealed by a metal barrier.